a) Field of the Invention
The present invention relates to a secretory component-containing composition separated from a milk or a whey.
The secretory component-containing composition of the present invention has anti-infectious effects and accordingly are useful in fields such as drugs, foods, cosmetics, feeds and the like.
b) Description of the Prior Art
A secretory component (hereinafter referred to as SC) is a glycoprotein synthesized in mammary glands and secreted into milk, and combines with immunoglobulin A (hereinafter referred to as IgA) which is one of immunoglobulins. The IgA which has combined with SC, is called secretory immunoglobulin A (hereinafter referred to as SIgA) and is contained in milk, particularly human milk in a relatively large amount. SIgA is the most important anti-infectious factor to babies, is not easily digested in the gastrointestinal tracts by protease, etc., and takes part in immune defense system by showing, for example, an agglutination action for antigens. This protease resistance of SIgA is known to be imparted by SC. Thus, SC plays an important role in the immune defense system in the body. Under such circumstances, there have long been made attempts to isolate SC from milk and examine the physical and chemical or biochemical properties. There are known various methods for isolating SC from milk. They include a method of first obtaining SIgA by DEAE type ion exchange chromatography and CM type ion exchange chromatography and then reducing the SIgA to obtain SC [e.g. K. Kobayashi, Immunochemistry, 8, 785-800 (1971)], and a method of obtaining free SC inherently present in milk. As the latter method, there are known (1) a method of subjecting a whey to ammonium sulfate fractionation and DEAE type ion exchange chromatography and then subjecting the unadsorbed whey portion to gel filtration chromatography, CM type ion exchange chromatography or phosphorylated ion exchange resin chromatography [J. E. Butler, Journal of Dairy Science, 55, 151-163 (1972); K. Kobayashi, Immunochemistry, 8, 785-800 (1971); R. S. Labib et al., Journal of Biological Chemistry, 251, 1969-1974 ( 1976)], (2) a method of subjecting a whey to DEAE type ion exchange chromatography, eluting the adsorbed component with a 0.01 M phosphate buffer solution of pH 7.6, and subjecting the eluate to CM type ion exchange chromatography [Enomoto et al., Digestive Organ and Immunity, 16, 146-150 (1986)], (3) a method of subjecting a whey to IgM-immobilized affinity chromatography [B. J. Underdown et al., Immunochemistry, 14, 111-118 (1977)], and methods which are slight modifications of the above methods (1) to (3).
In these methods, however, SC is isolated and purified only on laboratory basis, and there has not yet been proposed any method enabling the industrial production of SC-containing composition. The conventional methods have had further problems. That is, the whey from which SC has been removed by ammonium sulfate fractionation is difficult to find utilization; the DEAE type ion exchange chromatography requires a large amount of an ion exchange resin and is not suitable for industrial application; the gel filtration chromatography is not suitable for industrial application, either; the IgM-immobilized affinity chromatography is expensive, has restriction in washing and sterilization, and is not suitable at all for industrial application.